1. Field of the Invention
The present invention relates to a pixel structure and a method of fabricating the same, and more particularly, to a method of fabricating a pixel structure using a lower amount of masks and the pixel structure.
2. Description of the Prior Art
Thin-film transistors (TFTs) are commonly used as active components in active matrix display panels including active matrix liquid crystal displays and active matrix organic electroluminescent display panels. The conventional TFT including a gate, a source electrode, a drain electrode and a semiconductor layer which includes the channel of the transistor, can be formed through a manufacturing process including at least five lithography processes for defining the patterns of the semiconductor elements. The five lithography processes taken as examples are illustrated below. The first mask is used to define the first metal layer forming the scan line and the gate; the second mask is used to define the semiconductor layer; the third mask is used to define the second metal layer forming the data line, the source electrode and the drain electrode; the fourth mask is used to pattern a passivation layer to form the contact holes; and the fifth mask is used to define a transparent conductive layer forming the pixel electrode.
To reduce the number of masks and simplify the manufacturing process, the half-tone mask is commonly used to serve as the second mask when defining the pattern of the TFT elements. The half-tone mask includes a transparent substrate, a shielding region and a half-tone region disposed thereon. The shielding region is used to define the source electrode and the drain electrode, and the half-tone region is used to define the semiconductor layer underneath the source electrode and the drain electrode. Accordingly, the half-tone mask can substitute for the second mask and the third mask, i.e. only four lithography processes are needed for fabricating the TFT. However, the higher price of the half-tone mask compared to the general mask without the half-tone region disposed thereon is not beneficial, considering the manufacturing cost. Consequently, how to reduce the number of masks and simultaneously reduce the costs in the TFTs manufacturing processes is still an important issue in this field.